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Role of free Radicals

Male Infertility

Male infertility is caused by defective sperm function, which accounts for up to 24% of couples attending infertility clinics. A variety of malfunctions have been described, including abnormal flagella movement, failure to recognize the zone inhibition of sperm-oocyte fusion. ROS are important for normal physiological processes and are thought to be released only when sperm comes into contact with the oocyte, for facilitation of the acrosome reaction and binding to the oocyte to aid fertilization. However, elevated ROS levels have been identified in infertile males due to an imbalance between ROS production and antioxidant components. Reactive oxygen species initiate lipid peroxidation and accumulation of lipid peroxides in sperm membranes, causing a reduction in sperm motility and viability. ROS are not detectable in the ejaculate of normal fertile or azoospermic men.

Antioxidants are present in human sperm to protect against superoxide attack. SOD is an intracellular antioxidant enzyme, which is thought to leak into the seminal plasma. Sperm protection against peroxidative damage has been demonstrated in the presence of vitamin E, which was also reported to reduce the loss of sperm motility. Other studies have shown enhancement of sperm function in the presence of higher levels of vitamin E. Another study showed that oral supplementation of vitamin E in infertile men resulted in a significant improvement in the in vitro function of human sperm, which may have implications for patients using in vitro fertilization. Monitoring antioxidant levels in the ejaculate may detect deficiencies in antioxidant levels and aid the treatment of infertility with antioxidant supplementation.

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  5. Weinberg JB, Doty E, Bonaventura J, Haney AF. Nitric oxide inhibition of human sperm motility. Fertil Steril 1995; 64:408-413.

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